A water-soluble film using a polyvinyl alcohol-based resin is widely utilized in uses (unit packing uses) of individually packaging chemicals such as a detergent, a cleaning agent, a disinfectant, an insecticide, a herbicide, a fertilizer, a dye, and an agricultural chemical, uses of a hydraulic transfer film, and other uses.
In the uses of individually packaging chemicals, it is not necessary to measure in each time when using chemicals, and this is very convenient to users. Therefore, it is expected that market scale of a water-soluble film in the uses is expanding.
However, in the water-soluble film conventionally used, the film gradually colors in pale yellow by thermal history received during film formation of a film, and there has been a concern that commercial value of a product is impaired.
In view of the above, a technology of incorporating two kinds of a plasticizer and a sulfite in a water-soluble film has been attempted (e.g., see Patent Document 1).
This technology discloses that a water-soluble film that is hardly colored at the time of film formation and hardly increases in coloration with time even when being brought into contact with chemicals can be obtained by incorporating two kinds of a plasticizer and a sulfite.
However, in the technology of this document, coloration is improved, but there is a case that solubility is insufficient, and further improvement is desired.